One-pot synthesis and AFM imaging of a triangular aramide macrocycle

Macrocyclizations in exceptionally good yields were observed during the self-condensation of N-benzylated phenyl p-aminobenzoates in the presence of LiHMDS to yield three-membered cyclic aramides that adopt a triangular shape. An ortho-alkyloxy side chain on the N-benzyl protecting group is necessary for the macrocyclization to occur. Linear polymers are formed exclusively in the absence of this Li-chelating group. A model that explains the lack of formation of other cyclic congeners and the demand for an N-(o-alkoxybenzyl) protecting group is provided on the basis of DFT calculations. High-resolution AFM imaging of the prepared molecular triangles on a calcite(10.4) surface shows individual molecules arranged in groups of four due to strong surface templating effects and hydrogen bonding between the molecular triangles

Chelation of diamine ligands to zinc porphyrin monolayers amide-linked to glass

A pentafluorophenol active-ester porphyrin has been synthesised and covalently attached to an aminopropylsilylated glass surface by amide bond formation, Zinc is inserted into the surface-bound porphyrins and their interaction with amine ligands is investigated by UV-VIS spectroscopy, The high affinity of the zinc porphyrin monolayers for bidentate ligands such as 1,4-diazabicyclo[2.2.2]octane, 4,4'-bipyridyl and 1,3-di(4-pyridyl)propane demonstrates that the porphyrins are in close proximity on the surface and yet are not so tightly packed as to prevent ligand intercalation, Effective molarities of up to 0.35 mol dm(-3) are observed

A study on the molecular weight of the chloro-precursor polymer to MEHPPV

The observed molecular weight of the chloro-precursor polymer, 1, to poly[2-(2'-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] (MEHPPV) was found to decrease with decreasing polymer concentration when measured by gel permeation chromatography with the decrease probably being due to the dissociation of polymer aggregates or physical networks